CVE-2026-70658
pay-rails/pay: non-constant-time HMAC comparison in Paddle Billing webhook signature verifier
Pay is a payments engine for Ruby on Rails 6.0 and higher. Prior to 11.6.2, Pay::Webhooks::PaddleBillingController#valid_signature? in app/controllers/pay/webhooks/paddle_billing_controller.rb compares the computed 64-character SHA-256 HMAC with the attacker-controlled h1 token from the Paddle-Signature header using Ruby String#==. An unauthenticated remote attacker who can repeatedly submit requests to /pay/webhooks/paddle_billing and obtain sufficiently precise timing measurements can infer matching digest prefixes and recover a valid signature. A forged accepted webhook is enqueued through Pay::Webhooks::ProcessJob and can cause a host application to update billing state, provision paid features, record refunds, or trigger customer notifications. This issue is fixed in version 11.6.2.
| CWE | CWE-208 |
| Vendor | pay-rails |
| Product | pay |
| Published | Sep 14, 2026 |
| Last Updated | Sep 14, 2026 |
Get instant alerts for pay-rails pay
Be the first to know when new high vulnerabilities affecting pay-rails pay are published — delivered to Slack, Telegram or Discord.
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N